1. Field
The invention relates to data compression and decompression in a communication system and, in particular, to a system and method for improving Robust Header Compression (ROHC) efficiency.
2. Background
ROHC is an Internet Engineering Task Force (IETF) header compression framework that provides for high efficiency and robustness in wireless communication systems. Among other features, ROHC supports Real-time Transfer Protocol/User Datagram Protocol/Internet Protocol (RTP/UDP/IP) and UDP/IP compression profiles. The ROHC working group is also specifying support for a Transmission Control Protocol/Internet Protocol (TCP/IP) compression profile.
ROHC exhibits robustness, i.e., the ability to tolerate errors on the wireless links. ROHC is useable with multi-media applications and provides for header compression for various applications, protocols, and wireless technologies. Header compression is a technique to reduce the packet size transmitted over a link thereby increasing the link efficiency and throughput. Header compression is particularly useful on slow links or when packet sizes are small where a reduction in the header size results in a significant decrease in the header overhead. Header compression achieves this by leveraging header field redundancies in packets belonging to the same flow. In particular, many packet header fields such as source and destination addresses remain constant throughout the duration of a flow while other fields such as sequence numbers change predictably to allow header compression to transmit only a few bytes of header information per packet. FIG. 1 illustrates a typical ROHC compression/decompression block diagram 100 of IP/UDP/RTP headers over a communication link. Typically, reference copies of the full headers are stored at a ROHC compressor 102 and a ROHC decompressor 104 in order to reliably communicate and reconstruct original packet headers. There is a need in the art, however, for a system and method for improving ROHC efficiency by correctly interpreting change in increment of the RTP Timestamp field either due to silence suppression for a voice flow or due to a change in sampling/frame rate of a video flow.